Process for polymerizing butadiene and isoprene with haloaryllithium initiator



United States Patent 3,514,436 PROCESS FOR POLYMERIZING BUTADIENE ANDISOPRENE WITH HALOARYLLITHIUM INITIATOR William J. Trepka and Richard J.Sonnenfeld, Battlesville, Okla., assiguors to Phillips PetroleumCompany, a corporation of Delaware No Drawing. Filed Jan. 23, 1968, Ser.No. 699,771 Int. Cl. C0811 3/06, 3/10; C08f 3/16 US. Cl. 26094.2 2Claims ABSTRACT OF THE DISCLOSURE Preparation of haloaryllithiuminitiators by reacting a dihalobenzene or dihalonaphthalene with anorganolithium compound and elemental halogen or a mixed halogen compoundin the presence of a non-aromatic hydrocarbon diluent, which initiatorsare useful for the polymerization of isoprene and/ or butadiene toproduce rubbery polymer.

BACKGROUND OF THE INVENTION This invention relates to polymerizationinitiators and the polymerization of butadiene and/or isoprene usingsame. In another aspect, this invention relates to a process forpolymerizing butadiene, isoprene and mixtures thereof by contacting samewith certain haloaryllithium initiators used as polymerizationinitiators. In accordance with a further aspect, this invention relatesto a process for the preparation of haloaryllithium initiators fromdihalo aromatics and organolithium compounds in the presence of selectedhalogens and non-aromatic hydrocarbon diluent that are useful for thepolymerization of butadiene and/ or isoprene.

The production of monohaloaryllithium compounds such as3-brornophenyllithium is described in US. 3,215,- 679, Trepka. While anytype of hydrocarbon diluent can be utilized for the preparation of thesecompounds, nonaromatic diluents ordinarily have not been employed. Whenthese organolithium compounds are prepared in a diluent such ascyclohexane or n-pentane and subsequently used as initiators for thepolymerization of isoprene or butadiene, it has been found that theinitiator level needs to be relatively high in order to getpolymerization to occur.

In accordance with the invention, it has now been found thathaloaryllithium initiators can be prepared in a nonaromatic hydrocarbondiluent to give initiator materials which have excellent activity forthe polymerization of conjugated dienes such as butadiene and/ orisoprene. Quite surprisingly, it has now been found that when theseinitiators are employed for the polymerization of isoprene andbutadiene, much lower initiator levels can be used to give highermonomer conversion-than have beenfound operable with the known prior artmethods.

Accordingly, it is an object of this invention to provide Patented May26, 1970 SUMMARY OF THE INVENTION In accordance with the invention, aprocess is provided for the preparation of a polymerization initiatorfrom dihaloaryl compounds and organolithium compounds by reacting samein the presence of selected free halogens or mixed halogen compounds anda non-aromatic hydrocarbon diluent.

It has been found quite unexpectedly that the polymerization initiatorsformed above can be used at extremely low initiator levels, i.e., lessthan 2.5 millimoles per 100 grams of monomer for polymerization ofconjugated dienes such as butadiene and/or isoprene.

It has been further found that polymers formed from isoprene contactedwith the initiator prepared according to the invention have a highpercentage, generally in excess of 85 percent, and often up to 95percent or more, of cis-1,4-addition.

DESCRIPTION OF PREFERRED EMBODIMENTS The dihaloaryl compounds employedaccording to the invention are selected from 1,3-dihalobenzene or1,3-dihalonaphthalene wherein the halogen is selected from bromine,chlorine, or iodine. Representative examples of suitable dihaloarylcompounds include 1,3-dibromobenzene, 1,3-dibromonaphthalene,1,3-dichlorobenzene, 1,3-diiodonaphthalene, 3 bromochlorobenzene, 3iodochlorobenzene, 3-iodobromobenzene, 1,3-diiodobenzene, 1-bromo-3-chloronaphthalene, 1-iodo-3-bromonaphthalene, and the like.

The organolithium compounds that can be employed have the generalformula RLi, wherein R is an alkyl, cycloalkyl or aryl hydrocarbonradical, or combinations thereof, such as aralkyl, alkaryl, and thelike, containing from 1 to 12 carbon atoms. Examples of such compoundsare methyllithium, ethyllithium and n-butyllithiu'm, phenyllithium,cyclohexyllithium, cyclopentyllithium, n dodecyllithium, benzyllithium,4- phenylcyclohexyllithium, 4-cyclohexylphenyllithium, and the like.

The haloaryllithium initiators of the invention have the formula:

a process for the polymerization of butadiene and/ or isoprene.

It is yet another object of this invention to provide a process forproducing haloaryllithium initiators useful for the polymerization ofdiene monomers for producing rubbery polymeric products having improvedproperties. It is yet another object of this invention to provide animproved process for. producing polymers of..isoprene having a highpercentage of cis-1,4 addition.

It is a still further object of this invention, to provide apolymerization initiator which can be employed at lower initiator levelsthan with known prior art initiators. Other aspects, objects, and theseveral advantages of this invention will be apparent to those skilledin the art from the description and 'the appended claims.

' and mixtures of (A) and (B) wherein R and R are selected from'lithiumand a halogen, said halogen being the preparation of the initiators ofthe invention are se.

lected from parafiins and cycloparafiins containing from 3 4 to 10carbon atoms per molecule, preferably 4 to 7 carbon atoms per molecule,such as butanes, pentanes, hexanes, heptanes, cyclopentane,methylcyclopentane, cyclohexane, methylcyclohexane, and the like.

The molar ratio of dihaloaryl compound employed for Polymers such aspolyisoprene produced in accordance with this invention can becompounded in any conventional manner, utilizing vulcanizing agents,vulcanizing accelerators, accelerator activators, reinforcing agents,softeners, plasticizers, fillers and the like, and can be used theinitiator preparation to halogen or mixed halogen for the manufacture ofvehicle tires and in other applicompound present will be in the range of0.25:1 to :1. cations for natural rubber.

The amount of organolithium employed for the initiator preparation isthat which is suflicient to react with EXAMPLE I all the elementalhalogen or mixed halogen compound 10 Polymerization initiators wereprepared by reacting 1,3- with enough remaining to react with at least aportion dibromobenzene with variable amounts of n-butyllithium of the1,3-dihaloaryl compound to produce a haloaryland elemental iodine.3-bromophenyllithium was prepared lithium compound, as defined. It isnot necessary that all by reacting 1,3-dibromobenzene and n-butyllithium(no the 1,3-dihaloaryl compound be converted to haloaryliodine) and usedas a control initiator. The recipes were lithium. The molar ratio oforganolithium to halogen as follows: or mixed halogen compound will bein excess of 1:1 and generally will range from 1.05:1 to 15:1,preferably 2:1 Run 1 2 3 4 at? 1 d f .1 959 4 5 i8 92 t8 t8 etemperature emp oye or mitiator preparat1on wi 1 q q ewe/11911111110 9Sordinarily range from 32 to 212 F., preferably 86 to moles 5. 8 158 K6:1 4.711 4:1

The initiator can be prepared and the subsequent po- ""'i lymerizationcarried out in an inert atmosphere in the 2 2 2 2 0.1 0.13 0.13 0.09presence or absence, preferably presence, of a substantially inertdiluent. Suitable atmospheres include argon, helium, nitrogen, and thelike. Suitable polymerization The rea tl ns were conducted in anatmosphere of mdiluents include parafiins and cycloparaflins containingg Iodine Was charghd first, and then the Cyclohexfrom 4 to 10 carbonatoms per molecule, inclusive, exane. This mixture was agitated at atemperature of 122 amples of which include cyclohexane,methylcyclohexane, fOr One hour, after Which the li3-dihromohehlene Wasn-butane, n-hexane, n-pentane, n-heptane, isooctane, mixadded and thenthe butyllithium. The temperature was tures thereof, and the like.Aromatic hydrocarbons such ma ned at 122F. for tWO more hours to allowtime as benzene, toluene, xylene, and the like, can be used for for thereaction. The molar alkalinity of each reaction polymerization but arenot presently preferred. It is premixture was determined by titration ofa measured aliquot sently preferred to employ the same hydrocarbondiluent with 0.1 N HCl. The alkalinity was essentially that which forinitiator preparation as polymerization diluent. A was obtained by thereaction of each hydrolyzed polymhigher ciscontent of polymer isobtained when the poen'zation initiator aliquot with the 0.1 N HCltitrant. lymerization is conducted in a non-aromatic diluent. Each ofthe initiators was used in variable amounts for According to theinvention, an amount of haloarylliththe polymerization of isoprene. Therecipe was as follows: ium prepared according to the invention effectiveto cause 40 lsoprene, parts by weight 10o polymerization of 1sopreneand/or butadiene, which Cyclohexane, parts by weight 1000 amount is lessthan 2.5 gram milllmoles per 100 grams 1 Initiator, mhm. Variable ofmonomer, is contacted with monomer under polym- Temperature 0 F 158erization conditions, the polymerization temperature be- Time hours 2 or15 ing in the range of 100 C. to 150 0., preferably 75 "T'f u to 100 C.The pressure employed during polymerization mnhmfles Per 100 gramsmonomer' need be only that necessary to maintain the reaction mix- Thecyclohexane was charged first, after which the reture substantially inthe liquid phase. actor was purged with nitrogen, the monomer was intro-When isoprene is polymerized in accordance with this duced, and then theinitiator. At the conclusion of each invention, the polymer is obtainedin a solution and can polymerization the reaction was shortstopped withapbe treated with various reagents to produce functional proximately onepart by weight per 100 parts by weight groups by replacing the terminallithium atoms on the rubber of 2,2methylene-bis-(4-methyl-6-tert-butylphepolymer molecule. For example,polyisoprene in solution nol), employed as a 10 weight percent solutionin isocan be contacted first with carbon dioxide and then with propylalcohol. The polymer was coagulated in isopropyl an acid to replace thelithium atoms with a COOH alcohol, separated, and dried in a vacuumoven. Results group. Other functional groups which can be introduced arepresented in Table I.

TABLE I Initiator Poly Microstructure, Percent time, C0uv., Inh. Gel,Run No From Run Mhm hrs. percent Cis Trans Visc percent include -SH,--OH, and the like. Alternatively, the un- Microstructure, inherentviscosity, and gel data were quenched polymer solution can be treatedwith an alconot determined on the samples for which no values are hol orother reagent to inactivate the initiator and/or given. Thepolymerization time for runs 1 through 4 was precipitate polymer whichis then recovered without functwo hours. The data show that a 3millimole initiator tional groups. 75 level was required in control run4 to give a conversion as high as was obtained in run 3 made accordingto the invention. The polymerization time for runs 5 through 10 was 15hours. High conversions were obtained in runs 5 through 10, madeaccording to the invention.

'6 Each of the initiators was used in variable amounts for thepolymerization of isoprene. The recipe was the same as that given inExample I except for the polymerization iiIrlne which was 18 hours. Dataare presented in Table TABLE III Initiator Microstructure, percentConv., Inh Run N From Run mhm. percent Cis Trans Vise percent 1 2. 0 534 1 1. 7s 23 l 5 (control) 2 2. 5 19 6 (control) 2 2. 0 Trace EXAMPLE IIThese data show that iodine monochloride can be used Elemental brominewas employed instead of iodine for preparing polymerization initiators.The bromine was dissolved in cyclohexane to make a solution that was0.185 molar. The recipes were as follows:

Run 1 2 3 4 Cyclohexane, ml 68. 2 76. 5 85 0 93. 0 1,3-dibromobenzene,mmoles... 10 10 10 n-Butyllithium, mmoles 17. 5 12. 5 10 Bromine, mmoles.3. 75 2. 5 1. 25 0 BuLi: Blz mole ratio 4. 7:1 6:1 10:1DibromobenzeneiBrz mole ratio 2. 7:1 4:1 8:1 Temperature, F..., 122 122122 122 Time, hours 3 3 3 3 Molar alkalinity 0. 11 0. 11 0.08 0. 10

The reactions were conducted in an atmosphere of nitrogen. Cyclohexanewas charged first, then the dibromobenzene and thebutyllithium. Thebromine solution was added slowly to this mixture (while-it wasagitated. The temperature was maintained at .122 F. for three hours. Themolaralkalinity of each reaction mixture was determined bytitration of ameasured-aliquot with 0.1 N HCl.

Each of the initiators was used in variable amounts for. thepolymerization of isoprene. The recipe was the same as that given inExample I except that the polymerization time was 18 hours. Results arepresented in Table H.

instead of elemental halogen for the initiator preparation and that theinitiator is efiective at much lower levels for the polymerization ofisoprene than the control initiator which was prepared in the absence ofiodine monochloride.

EXAMPLE IV An initiator was prepared by reaching 1,3-dibromobenzene,butyllithium, and elemental iodine in the presence of n-pentane as thediluent instead of cyclohexane. The recipe was as follows:

i This initiator and that prepared according to run 2 of Example I(cyclohexane used as diluent) were employed TABLE II InitiatorMicrostructure, ercent Conv., p Inh. Gel, Run No. From Run mhm. percentCis Trans Visc. percent 1 1. 5 1 1. 2 1. 5 2 1. 75 5 3 1. 75 6(control)... 4 1. 5 7 (control) 4 1. 75

These data show that lower initiator levels can be employed to obtainhigher conversions to polymer than can be used when the initiators areprepared in the conven tional manner, i.e., without addition ofelemental halogen.

EXAMPLE :III

Iodine monochloride was employed instead of elemental halogen forpreparing a polymerization initiator. The diluent was charged first,then the iodine monochloride, the 1,3-dibromobenzene, and then-butyllithium. A control initiator was prepared without the iodinemonochloride. The recipes were as follows:

for the polymerization of isoprene. The recipes were as follows.

A series of runs was made using each initiator. The conversion for runsmade according to recipe 1 ranged from 87 to 94 percent and the ciscontent ranged from 89 to 93 percent. The conversion for runs madeaccording to recipe 2 ranged from 51 to 92 percent and the cis contentranged from 84 to 93 percent. Products prepared according to recipe 1were blended to obtain a sample for evaluation. Inherent viscosity ofthe blend was 5.3. Likewise, products prepared according to recipe 2were blended. Inherent viscosity of this blend was 4.2.

Each of the polymer blends was compounded in a tread stock recipe andalso in a guru stock recipe, cured, and physical properties determined.

TABLE IV Run 1 2 Tread stock recipe, parts by weight Pol 100 100 Highabrasion furnace black 50 50 Zinc oxide 3 3 Stearie acid 3 3 Flexamine 11 Flexzone 3C 2 2 Aromatic oil (Plnlrich 5 5 Vultrol 1 1 Sulfur 2. 25 2.25 NOBS Special 0. 65 0. 65

Cured 30 minutes at 293 F.

Compression set, percent 21.0 21. 5 300% Modulus, p.s.i 1, 370 1, 340Tensile, p.s.i 4, 030 3, 950 Elongation, percent 615 615 Maximum tensileat 200F., p.s. 2, 420 2, 310 AT, F 40. 6 43 Resilience, percent. 72. 170. 8 Shore A hardness 58 57. 5

Gum stock recipe, parts by weight Cured 30 minutes at 293 F.

Tensile, p.s.i 4,150 4, 200

Physical mixture containing 65 percent of a complex diarylamineketonereaction product and 35 percent of N,N-d1phenyl-p-phenylenediamine.

( N-isopropyl-N-phenyl-p-phenylenediamine.

( N-nitrosodiphenylamine.

( N-oxydiethylene-2-benzcthiazolesulfenamlde.

( N-cyelohcxyl-Z-benzothiazolesulfenamide.

( High temperature reaction product of diphenylamine and acetone.

The data show that the polyisoprene prepared using the initiators ofthis invention gave vulcanizates with excellent properties in both treadstock and gum stock recipes. The data also demonstrate that n-pentanecan be employed as a diluent for preparing the initiators.

We claim: 1. A process for the polymerization of butadiene and/orisoprene monomers which consists of contacting at least one of saidmonomers with a haloaryllithium initiator at a temperature in the rangeof C. to C., the amount of initiator present being less than 2.5 grammillimoles of haloaryllithium per 100 grams of monomer to bepolymerized, a pressure sufiicient to maintain the polymerizationmixture substantially in the liquid phase, and in a hydrocarbon diluentselected from paraffins and cycloparafiins, said initiator consisting ofhaloaryllithium compounds having formulas (A) and (B) defined in thespecification formed upon reacting (a) a dihaloaryl compound selectedfrom 1,3-dihalobenzene and 1,3-dihalonaphthalene wherein the halogensubstituent is selected from bromine, chlorine, and iodine, (b) anorganolithium compound in the presence of (c) an elemental halogen or amixed halogen compound again selected from chlorine, bromine, or iodine,and a hydrocarbon diluent selected from paraflins and cycloparaifins.

2. A process according to claim 1 for polymerization wherein saidmonomer is isoprene, said dihaloaryl compound is 1,3-dibromobenzene,said organolithium compound is n-butyllithium, said halogen is selectedfrom elemental iodine, elemental bromine and iodine monochloride, andsaid hydrocarbon is selected from cyclohexane and n-pentane.

References Cited UNITED STATES PATENTS 3,312,680 4/1967 Kahle 260-94.23,393,189 7/1968 Trepka et al 26094.2 3,429,829 2/ 1969 Kahle 252431OTHER REFERENCES Copending application Ser. No. 634,454 applicantsTrepka and Sonnenfeld.

JOSEPH L. SCHOFER, Primary Examiner W. F. HAMROCK, Assistant ExaminerUS. Cl. X.R. 252431; 260-665

